The effect of glutamine (0.6/kg/day) and creatine monohydrate (5g/day) on muscle strength will be evaluated in a multi-center randomized double-blind placebo-controlled 3-arm study. Ambulant children aged 5-10 years with an established DMD diagnosis will be studied. Patients will undergo 2 screening evaluations within 2 weeks. Patients will be randomized into treatment groups on the second screening visits, followed by a 6-month treatment period. During the treatment period, patients will be evaluated at monthly intervals. The primary endpoints are percentage change in average muscle strength score and QMT performance for specific muscle groups. Secondary endpoints include timed function tests, functional grades for arms and legs, and pulmonary function tests.